Hydrosilylation of trivinylcyclohexane and similar alkenyl compounds with multiple carbon-carbon unsaturated bonds has been disclosed in, for example, U.S. Pat. Nos. 5,166,298, 6,278,011, 6,265,497, and 6,278,011. The emphasis in these patents has been on complete reaction of all double bonds. Accordingly, in the reactions disclosed in these patents, the molar ratios of the silicon hydride groups in the silyl hydrides relative to the carbon-carbon double bonds in the polyunsaturated compounds were greater than 1.0. In addition, long reaction times were often used to ensure complete hydrosilylation of the unsaturated groups.
Recently, the need for selective mono-hydrosilylation product of 1,2,4-trivinylcyclohexane has surfaced. Illustratively, U.S. Pat. No. 7,696,269 discloses that (2-trialkoxysitylethyl)divinyl-cyclohexane, which is a mono-hydrosilylation product of 1,2,4-trivinylcyclohexane, can be used as a key intermediate in the synthesis of sulfur silanes useful for imparting low rolling resistance to automobile tires.
Unfortunately, the selectivity of conventional precious metal based catalysts towards mono-hydrosilylation is normally less than desirable. For example, even when a sub-stoichiometric amount of silane is used in the platinum catalyzed hydrosilylation of trivinylcyclohexane (silane:vinyl ratio of 0.8:1), a mixture only containing about 50 weight percent of the desired mono-hydrosilylated product and about 30 weight percent of the bis-hydrosilylated derivative is produced.
Non-precious metal based hydrosilylation catalysts have been disclosed in the art. Illustratively, Wu et al. reported in J. Am. Chem. Soc. Vol 132 (2010) 13214 that low valent iron iminopyridine complexes catalyze 1,4-hydrosilylation of 1,3-dienes.
U.S. Patent Application Publication No. 20110009565 discloses non-precious metal terpyridine complexes and their use as hydrosilylation catalysts. U.S. Patent Application Publication No. 20110009573 discloses non-precious pyridinediimine complexes and their use as hydrosilylation catalysts. The contents of the '565 and the '573 publications are incorporated herein by reference in their entireties. Although trivinylcyclohexane is among the unsaturated compounds mentioned in these two applications, the applications are silent regarding mono-hydrosilylation selectivity of the catalysts to polyunsaturated compounds such as trivinylcyclohexane.
Accordingly, there is a continuing need in the hydrosilylation industry for selectively producing mono-hydrosilylated product from a polyunsaturated compound and a silyl hydride. The present invention provides one answer to that need.